This invention relates to methods for delivering and deploying an endovascular graft within the vasculature of a patient and more specifically to a modular grafting system used to treat vasculature.
It is well established that various fluid conducting body or corporeal lumens, such as veins and arteries, may deteriorate or suffer trauma so that repair is necessary. For example, various types of aneurysms or other deteriorative diseases may affect the ability of the lumen to conduct fluids and, in turn, may be life threatening. In some cases, the damage to the lumen is repairable only with the use of prosthesis such as an artificial vessel or graft.
For repair of vital lumens such as the aorta, surgical repair is significantly life threatening or subject to significant morbidity. Surgical techniques known in the art involve major surgery in which a graft resembling the natural vessel is spliced into the diseased or obstructed section of the natural vessel. Known procedures include surgically removing the damaged or diseased portion of the vessel and inserting an artificial or donor graft portion inserted and stitched to the ends of the vessel which were created by the removal of the diseased portion. More recently, devices have been developed for treating diseased vasculature through intraluminal repair. Rather than removing the diseased portion of the vasculature, the art has taught bypassing the diseased portion with a prosthesis and implanting the prosthesis within the vasculature. An intra arterial prosthesis of this type has two components: a flexible conduit, the graft, and the expandable framework, the stent (or stents). Such a prosthesis is called an endovascular graft.
It has been found that many abdominal aortic aneurysms extend to the aortic bifurcation. Accordingly, a majority of cases of endovascular aneurysm repair employ a graft having a bifurcated shape with a trunk portion and two limbs, each limb extending into separate branches of vasculature. Currently available bifurcated endovascular grafts fall into two categories. One category of grafts are those in which a preformed graft is inserted whole into the arterial system and manipulated into position about the area to be treated. This is a unibody graft. The other category of endovascular grafts are those in which a graft is assembled in-situ from two or more endovascular graft components. This latter endovascular graft is referred to as a modular endovascular graft. Because a modular endovascular graft facilitates greater versatility of matching the individual components to the dimensions of the patient's anatomy, the art has taught the use of modular endovascular grafts in order to minimize difficulties encountered with insertion of the devices into vasculature and sizing to the patient's vasculature.
Although the use of modular endovascular grafts minimize some of the difficulties, there are still drawbacks associated with the current methods. Drawbacks with current methods can be categorized in three ways; drawbacks associated with delivery and deployment of the individual endovascular graft components, drawbacks associated with the main body portion, and drawbacks associated with securing the limb portions to the main body portion.
The drawbacks of current methods of joining the limb components of a modular endovascular graft to the main graft component include disruption of the junction over time and leakage at the connection site of the components. The junctions conventionally used in the art may depend upon friction between the overlapping components to hold them in place relative to each other. In other cases, the overlapping portion of one component may be adapted to form a frustoconical shape compatible with the overlapping portion of the other component. This serves to enhance the frictional connection between the components and provides a degree of mechanical joining. However, certain of these junctions relies primarily upon radial pressure of a stent to accomplish the joint-seal between the components and may be disrupted by the high shear forces generated by the blood flow and shrinkage of the aneurysm sac during the natural healing process. Once the junction between modular components of an endovascular graft has been disrupted, blood may flow into the aneurysm sac, a condition known as “endoleak” that can cause repressurization of the aneurysm that leads to death or severe injury to the patient.
Furthermore, even if the junction between the components is not disrupted, leakage may still occur. The limb components used in friction-fit designs often are composed of a stent-like exoskeleton over a layer of graft material. This means that the seal is between the graft material of the limb support portion of the main body component and the stent structure of the limb component. Since the stent is not a closed structure, it is still possible for blood to leak between the limb component and the main body component.
With regard to the method of joining the limb components of a modular endovascular graft to the main body component, there therefore exists a need for structure and a method that provides a leak-proof seal that will not be disrupted by blood flow or physiologic remodeling over time.
The devices and methods of the present invention address these and other needs.